Sudden Cardiac Death &

Ventricular Fibrillation

Sudden cardiac death (SCD) is an unexpected natural death caused by loss of heart function within a short time period, generally less than one hour from the onset of symptoms. Also known as cardiac arrest, it accounts for approximately 300,000 to 400,000 deaths annually in the United States. Most cases of SCD are related to cardiac arrhythmias (abnormal heart rhythms).

The most severe arrhythmia condition is ventricular fibrillation. This condition sends erratic electrical impulses that stop the heart by causing the ventricles to quiver instead of pump blood. Ventricular fibrillation is the most common cause of sudden cardiac death.

It is important to understand the difference between SCD and a heart attack (myocardial infarction). A heart attack occurs when blood flow to the heart stops; the heart does not receive the necessary oxygen-rich blood it needs due to a block or blockage that may build up over time. Sudden cardiac death, on the other hand, occurs when the heart stops; the electrical current to the heart malfunctions, the heartbeat is irregular and the heart suddenly stops beating. It is no longer able to send much-needed blood to the brain, lungs and other vital organs.

Symptoms of Sudden Cardiac Death
In many cases, sudden cardiac death occurs without prior symptoms. When symptoms present, they may include the following: 

  • Racing heartbeat 
  • Feeling dizzy 
  • Not breathing or only gasping 
  • Sudden loss of consciousness/nonresponsive 
  • No pulse


You can reduce your risk of SCD by adhering to arrhythmia medications. Also, if you have known risk factors, such as family history or have a known arrhythmia, an implantable cardioverter defibrillator (ICD) can be surgically implanted to correct any possibly life-threatening conditions.

Treating Sudden Cardiac Death
Because the onset of SCD is so rapid, and many victims are not known previously to suffer from heart disease, it is considered extremely hard to prevent and treat. If symptoms of SCD appear, call 911 immediately. Cardiopulmonary resuscitation (CPR) should be administered right away while waiting for medical assistance. Emergency vehicles and many public places now have defibrillators available for this urgent use. It is essential to get the heartbeat back to a regular rhythm, pumping the necessary blood throughout the body.


Our physicians at Houston Methodist specialize in managing heart arrhythmias at the following convenient locations.